Fluorogenic substrate based on the C-terminus derivatization of ubiquitin with 7-amino-4-trifluoromethylcoumarin (AFC). Similar to ubiquitin-AMC, this is an exquisitely sensitive deubiquitinating enzyme substrate and is useful for studying ubiquitin C-terminal hydrolytic activity when detection sensitivity or continuous monitoring is essential. The fluorophore has a larger Stokes radius than AMC which is useful to reduce compound interference in HTS assays.